The Liber Floridus (1121), composed, written and illustrated by Canon Lambert of Saint-Omer, is the earliest illustrated encyclopedic compilation of the Latin West. Its autograph (Ghent, University Library, MS 92), a masterpiece of Romanesque book art and one of the most complicated manuscripts ever made, has been studied by the author for almost half a century. The present book is the culmination of this research and provides a detailed codicological and textual analysis, showing how this wonderful book was put together and which are the hidden ideas Lambert sought to develop in its hundreds of texts and pictures dealing with astronomy, geography, natural history, history, religion and countless other subjects. The book is illustrated with some 100 colour reproductions and numerous diagrams of quire structures. Three tables help the reader to understand the author's argument, and full indices give access to the text and provide the basis for further investigation of individual chapters and pictures.